For an essay, you will need to establish your aim, and the overall direction of the paper.
Just because the thesis statement is the foundation of the experiment, it does not mean that you need to do it first.
With more complex subjects, it’s tempting to make the scope of your paper as large as possible.
But resist writing a paper that combines too many loosely related concepts instead of selecting just a single thread to explore thoroughly.
Unless you are documenting research or writing a purely descriptive essay, you will be basing the paper around this thesis statement, so it needs to be well thought out.
If an assignment asks you to analyze, argue, compare and contrast, establish a cause or otherwise interpret, the chances are that you will need to base it around a clearly defined thesis statement.
For most papers, you want to discuss one concept and elaborate on that, otherwise the paper quickly loses focus.
Too many smaller theses will likely end up confusing the reader or weakening the overall effect.
A thesis statement is a sentence that states what you want your paper to show, what you want to convince your readers of after having read your thesis.
This is the foundation of the entire work and informs the reader exactly what you wish to achieve with the paper, and what you wish to prove or disprove.